The Guard quickly went to work, arresting, detaining, and interrogating Corellian terrorist suspects. One such suspect was Ailyn Habuur, a bounty hunter who was arrested by a Guard unit on suspicion of planning an assassination, and was repeatedly tortured by the GAG. Girdun got into a heated argument with Guard captain Lon Shevu over the torture methods utilized by the Galactic Alliance Guard. Girdun, used to using more violent means of interrogating subjects, did not agree with the more passive treatment advocated by Shevu, and the two got into a confrontation. Shevu stood firm, and Girdun eventually walked away, frustrated with Shevu's stubbornness. Shevu left the interrogation of Habuur to Girdun, a move that bewildered Jedi apprenticeBen Skywalker, who believed that he was too cruel to be trusted with Habuur's treatment.[1]

Girdun's time in charge of Ailyn Habuur's interrogation was not long, as Jacen Solo personally relieved him of that duty citing unacceptably poor results. Solo took over her interrogation himself, and ended up killing her unintentionally. Girdun and Shevu tried to treat her medically to no avail, and she was pronounced dead at the scene. Girdun, having previously interrogated a Corellian agent arrested along with Habuur, was assigned to question three other Corellians who had been detained along with the bounty hunter. It was hoped that he could obtain more information about Habuur's target. However, before he could get to work, Skywalker identified Habuur's target as Solo's father Han Solo due to surveillance images on Habuur's datapad, eliminating the need for Girdun to interrogate the other Corellians.[1]

As the war raged on, the removal of Corellian president Dur Gejjen was deemed necessary to the Galactic Alliance war effort. Jacen Solo assigned Ben Skywalker to assassinate Gejjen, and Girdun soon began teaching the boy to track his future target. While teaching Skywalker how to use the surveillance equipment, he was alerted to a recorded conversation between Gejjen and Galactic Alliance Chief of State Cal Omas, picked up about four hours earlier. The conversation was a cease-fire negotiation between Corellia and the Alliance, but Gejjen wanted Solo and Galactic Alliance Defense ForceAdmiralCha Niathal removed from office. Girdun, knowing that Gejjen now had to be stopped due to his desires to remove Solo and Niathal, quickly reported this conversation to Solo.[3]

Because of his dealings with Gejjen, Cal Omas was quickly removed from the office of Chief of State of the Galactic Alliance, replaced by Cha Niathal. Once Omas had officially been removed from office, Heol Girdun, Lon Shevu and fellow GAG officer Jori Lekauf immediately began training Skywalker to assassinate Dur Gejjen when the time came. Skywalker soon went to the Deep Core planet Vulpter to kill Gejjen after a negotiation with the Alliance. Skywalker successfully assassinated Dur Gejjen, although Jori Lekauf lost his life following a fight with security.[3]

With Dur Gejjen eliminated, Solo soon turned his attention toward Chief of State Cal Omas, having him eventually imprisoned, where Omas committed suicide. Around the same time as the Chief of State's death, Jacen Solo and Cha Niathal rose to power to govern the Galactic Alliance as a duumvirate.[4] After the change in power, the Galactic Alliance Intelligence organization was placed under the command of the GAG. Due to his experience with the intelligence agency, Girdun was appointed the new commander of Galactic Alliance Intelligence.[2]

After the assassination of Gejjen, Jacen Solo, having taken up the Sith mantle of Darth Caedus, dueled and killed Jedi MasterMara Jade Skywalker on the planet Kavan, in the Hapes Cluster. Skywalker's killer was left unknown to most, and Skywalker's son, Ben Skywalker, and Lon Shevu undertook an investigation of their own. The duo decided that they needed to examine Skywalker's starfighter, which was stored in the GAG hangar under Girdun's watch. While the two tried to inspect Skywalker's StealthX, they were happened upon by Girdun. However, he didn't suspect a thing, and allowed Shevu and Skywalker to get away.[5]

Because of his long history in intelligence, specializing in interrogating prisoners, Girdun was accustomed to using harsher methods on prisoners. To Ben Skywalker, he seemed callous and cruel to the prisoners,[1] and when Ailyn Habuur was tortured to death in front of him, he was only dismayed, not upset, over the death of the prisoner.[2] Although higher-ranked Galactic Alliance officers were disappointed in Girdun's service to the GAG,[1] his long history of work in various intelligence services made him invaluable, eventually fueling his rise to commander of Galactic Alliance Intelligence.[2]

As Jacen Solo's power in the Alliance military grew, Girdun began to wonder about Solo's motivations, openly raising questions about the Jedi's actions.[2] Despite his skepticism of Solo, Girdun harbored a slight fear of him after hearing some of the stories told about his brutality.[5] Solo, along with most of the GAG, generally considered Girdun a weaker leader than his colleague, Lon Shevu, and he was generally disliked among the GAG officers.[1] Among the leaders of the GAG, Girdun was seen as overly ambitious, and desperate for a promotion within the military.[3]